FULL PAPER
RETENTION INDEX (RI) OF Tc-99m MIBI THYROID
SCINTIGRAPHY, ULTRASONOGRAPHY (USG), AND
FINE-NEEDLE ASPIRATION CYTOLOGY (FNAC) IN THE
ASSESSMENT OF THYROID NODULE
ID Mulyanto, AHS Kartamihardja, and JS Masjhur. Department of Nuclear Medicine
Faculty of Medicine, UniversitasPadjadjaran/Dr. HasanSadikin General Hospital, Bandung, Indonesia
Oral Presentation on
RETENTION INDEX (RI) OF Tc-99m MIBI THYROID
SCINTIGRAPHY, ULTRASONOGRAPHY (USG), AND
FINE-NEEDLE ASPIRATION CYTOLOGY (FNAC) IN THE
ASSESSMENT OF THYROID NODULE
ID Mulyanto, AHS Kartamihardja , JS Masjhur . Department of Nuclear Medicine
Faculty of Medicine, UniversitasPadjadjaran/Dr. HasanSadikin General Hospital, Bandung, Indonesia
Oral Presentation on
10th Asia and Oceania Thyroid Association Congress Bali, Indonesia, 21-24 October 2012
Abstract
Background: Thyroid nodules are frequently encountered in clinical practice and most of which are benign in nature.However, it is still a challenge to effectively distinguish
malignant nodules from benign since FNAC as the primarydiagnostic tool does not give a definitive diagnosis in 10 – 42% of case (indeterminate results). This prospective study wasdesigned to appraise the significance of Tc-99m MIBI scintigraphy using retention
index parameter, USG, and FNAC in differentiating benign from malignant thyroid nodules.
Material and Method: Single injection, dual phase (15 and 120 minutes) thyroid scintigraphy using 370-555 MBq Tc-99mMIBI was performed in all participants. All
participants also underwent ultrasonography, FNAC, and surgery.
>0.58 as malignant thyroid nodule, the sensitivity, specificity, NPV, PPV, andaccuracy for Tc-99m MIBI were 87.5%, 70.6%, 92.3%, 58.3%, and 80% respectively. Sensitivity,
specificity, NPV, PPV,and accuracy for USG were 87.5%, 52.9%, 90%, 46.7%, and 64%. FNAC showed 14 benign nodules, 6 indeterminate, and 5malignant nodules. Diagnostic
performance of Tc-99m MIBI thyroid scintigraphy was not significant different from USG,but RI was capable to detect 5 out of 6 (83%) participants with indeterminate FNAC.
Conclusion: RI of Tc-99m MIBI scintigraphy may be useful in the assessment of thyroid nodule, especially those withindeterminate FNAC result.
Introduction
Thyroid nodules are frequently encountered in clinical practice and most of which
are benign in nature. It could be simply distinguish from normal surrounding tissue by palpation or using ultrasound (USG). According to Revised American Thyroid
Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer 2009, the incidence of thyroid nodule is 5% in female and
1% male. Incidence was higher if (19-67%) if using USG to examine the thyroid nodule.1-3 Thyroid cancer was found in 5-10% patients with thyroid nodule, while rest of them were benign. Gold standard for the diagnosis of thyroid nodule is tissue
histopathologic examination taken from surgery or biopsy in non-operable nodule. There quite high number of patient was underwent unnecessary surgery. Surgery is a high cost
USG, thyroid scan and fine needle aspiration cytology (FNAC) are diagnostic modalities could be use to help clinician to differentiate cancer from benign thyroid
nodule.2-4 There is no pathognomonic characteristic from USG test alone can be used to for the diagnosis of thyroid cancer.2 Variation of diagnostic result of USG are operator
dependent as well as specification of instrument and the criteria of diagnosis.5-7 99m
Tc pertechnetate thyroid scan is one of diagnostic modality to evaluate thyroid nodule. Thyroid scan has low specificity test, since only 5-15% of cold nodule observe
from thyroid scan are malignant.2-4
FNAC is a specific test for the diagnosis of thyroid cancer. This modality has high
negative predictive value.2,3,8However, it is still a challenge to effectively distinguish malignant nodules from benign since FNAC as primarydiagnostic tool does not give a definitive diagnosis in 10 – 42% of case (indeterminate results).
Technetium-99m hexakis-2-methoxyisobuthylisonitrile (99mTc-MIBI) can be used as radiopharmaceutical for thyroid scan. This radiopharmaceutical can be accumulated in
cancer cells.9-11
The aim of this study was to evaluate the significance of 99mTc-MIBIscintigraphy
using retention index parameter, USG, and FNAC in differentiating malignant from benign thyroid nodules.
Material and Method
This descriptive, comparative, and prospective study wasdesigned to evaluate the
significance of 99mTc-MIBIscintigraphy using retention index parameter, USG, and FNAC in differentiating malignant from benign thyroid nodules. This study was
was approved by Health Research Ethics Committee, Faculty of Medicine UniversitasPadjadjaran. Subjects were patient with single thyroid cold nodule based on 99m
Tc pertechnetate thyroid scan, normal thyroid function and scheduled to be operated or biopsy. Pregnant and breast feeding patients, and patient with parathyroid adenoma were
excluded. Histopathology test post surgery was used as gold standard.
Ultrasonography
Thyroid USG was done by using linear probe to produce gray scale images and read by radiologist. Kang score was used to evaluate thyroid nodule.
99m
Tc-MIBI thyroid scan
Static thyroid scan was done from anterior projection using gamma camera with
energy setting 140 keV, window width 20%, 4 x zoom, 15 minute and 2 hour after injection of 370-555 MBq (10-15 mCi) 99mTc-MIBI. Region of interest (ROI) was
manually draw over 2 images.
All subject also underwent FNAC, and surgery.
Statistic analysis
Statistic analysis was used to compare retention index of 99mTc-MIBI between
subject with malignant and benign thyroid nodule. Diagnostic test using 2X2 table was applied to evaluate diagnostic performance of retention index of 99mTc-MIBI, USG and
Results
Total subjects included in this study was 25, consist of 24 female and 1 male, aged 16-17 years old. Diameter of thyroid nodule based on USG was 9-130 mm. Malignant
thyroid nodule (papillary and follicular) was observed in 8 subjects, and benign (adenomatous, colloid goiter and thyroiditis) in 17 subjects. Using t-test analysis, there is
no significant different (p>0.05) between characteristic subject with malignant and benign nodule.
Table 1. Comparation of diagnostic value of retention index of 99mTc-MIBI, USG and FNAC in subject with malignant and benign thyroid nodule
Nodule Characteristic Sensitivity Specificity accuracy
Diagnostic Test Malignant Benign (%) (%) (%) benign thyroidnodule (0.58±0.17). Using cut-off > 0.58 of retention index for malignant
thyroid nodule, the sensitivity, specificity, NPV, PPV, andaccuracy for 99mTc-MIBI were 87.5%, 70.6%, 92.3%, 58.3%, and 80% respectively. Sensitivity, specificity, NPV, PPV,and accuracy for USG were 87.5%, 52.9%, 90%, 46.7%, and 64%. Sensitivity,
significant different from USG, but retention index was capable to detect 5 out of 6 (83%) participants with indeterminate FNAC. Diagnostic performance of combination
between retention index of 99mTc-MIBI and FNAC showed sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 100%, 93.3%,
85.7%, 100% and 94.7% respectively.
Tabel 2. Kappa score of retention index of 99mTc-MIBI, USG and FNAC in subject with malignant and benign thyroid nodule
Histopathologic test
Diagnostic test Malignant Benign Kappa value
RI* 99mTc-MIBI 0.51
Kappa analysis was done to evaluate concordance between retention index of 99m
Tc-MIBI (k=0.51), USG (k=0.38 and FNAC (k=0.33) with histopathologic test. K value of for retention 99mTc-MIBI was higher compared to USG and FNAC. (table 2)
Discussion
Proportional test of characteristic using t-test between subject with malignant and benign thyroid nodule showed no significant different with p >0.05, so those 2 groups could be compared.
using retention index as parameter, 99mTc-MIBI scan was done as early and late images. Retention index was calculated by comparing number of 99mTc-MIBI uptake from 2
images.12,13
Retention index 0.39 was found in 1 subject with malignant thyroid nodule. This
discrepancy between low retention index and malignancy may be due to the diameter of nodule was relatively small (26 mm). This study showed 5 subjects with retention index 0.68-0.93 were benign. This discrepancy could be due to several factors such as, diameter
of tumor relatively bigger, with high vascularity and proliferation.14 All those 5 subjects underwent Doppler USG to evaluate vascularity. The results showed no significant
different compared to subject with benign thyroid nodule. Proliferation index could not be determined, since Ki-67, PCNA and MIB-1 were not done.
Diagnostic performance of retention index of 99mTc-MIBI, USG and FNAC in
thyroid cold nodule based on sensitivity, specificity, positive predictive value, negative predictive value and accuracy were not significantly different. Kappa analysis showed
that kappa value of retention index of 99mTc-MIBI, USG and FNAC were 0.51, 0.38 and 0.33 respectively. Retention index of 99mTc-MIBI has moderate degree of agreement with
histopathologic test, while USG and FNAC had poor degree of agreement.
Retention index of 99mTc-MIBI has higher sensitivity compared to 2 other modalities and FNAC has higher specificity, by combining retention index of 99mTc-MIBI
with FNAC can increase diagnostic value. Cold nodule with indeterminate or positive malignant based on FNCA and retention index of 99mTc-MIBI > 0.58 are malignant
nodule. Cold nodule with indeterminate or benign based on FNCA and retention index of 99m
specificity, positive predictive value, negative predictive value and accuracy were 100%, 93.3%, 85.7%, 100% and 94.7% respectively.
Conclusion
Retention index of 99mTc-MIBIscan was a useful test to differentiate malignant from
benign thyroid nodule, particularly to patient withindeterminate FNAC result.
Diagnostic performance of retention index of 99mTc-MIBI was better compared to
USG and FNAC in differentiating malignant from benign thyroid nodule.
References
1. Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer 2009;19:1167-8.
2. Schlumberger M and Pacini F. Thyroid Tumor 3rd ed. Thyroid Nodule. Paris
2006:13-14.
3. Yeung MJ and Serpell JW. Management of the Solitary Thyroid Nodule. The
Oncologist 2008:13:105-12.
4. Albar ZA, Tjindarbumi D, Ramli M, Lukito P, Reksoprawiro, Handoko et al.
Protokol Peraboi 2003. Protokol Penatalaksanaan Tumor/Kanker Tiroid, Bandung 2004: 22.
5. Moon WJ, Jung SL, Lee JH, Na DG, Baek JH, Lee YH et al. Benign and malignant thyroid nodules: US differentiation-multicenter retrospective study. Radiology
6. Papini E, Guglielmi R, Bianchini A, Crezcenzi A, Taccogna S, Nardi F et al. Risk of malignancy in non-palpable thyroid nodules: predictive value of ultrasound and
color-doppler features. J. Clin Endocrinol Metab 2002;87:1941-6.
7. Cappelli C, Castellano M, Pirola I, Cumetti D, Agosti B, Gandossi E, et al. The
predictive value of ultrasound findings in the management of thyroid nodules. Q J Med 2007;100:29-35.
8. Suen KC. Fine-needle aspiration biopsy of the thyroid. CMJ 2002;167(5):491-5.
9. Vallabhajosula S. Radiopharmaceuticals in oncology. In Khalkhali I, Maublant JC, Goldsmith SJ. Nuclear oncology diagnosis and therapy. Lippincott Willims and
Wilkins. Philadelphia, 2001: 40.
10.Moretti JL, Hauet N, Caglar M, Rebillard O, Burak Z. To use MIBI or not to use MIBI? That is the question when assessing tumor cells. Eur J Nucl Med Mol Imaging
2005;32:836-42.
11.Schillaci O, Bucombe JR. Breast scintigraphy today: indications and limitations. Eur
J Nucl Med Mol Imaging 2004;31:35-45.
12.Camarthy M, and Harald S. Use of myocardial imaging agents for tumor diagnosis- a
success story? Semin Nucl 6Med 2010;40:257-70.
